How to use API to get DataType and Data Field configuration

I will be using the API to assemble components. I found the discussion describing exactly how I need to make the call to do the assemble, including the Component Data Fields to be collected. However, I can't find out how to get the configuration of the Data Fields to be collected. I can find the DataTypeRef in the Material (component) and the BOM Component line items, but I can't find the Package/Classes/Interface/APIs to use that Reference to get the list of Data Fields that are configured for collection at assemble time. any directipon would be appreciated.